A quick tip I discovered and would like to share:
Most regular lights in Sims 3 have two disadvantages:
1) They give off an ugly, artificial color of light
2) They clutter the screen, often getting in the way of your view of your sims.
Invisible LightsAfter a lot of frustration and experimenting, I found out that there are invisible light sources to be found in the catalog, under the 'Debug' category. To access this, you need to press CTRL + C, then type 'Testingcheatsenabled on' and then 'Buydebug on.' A new category will open up with lots of items not normally available to you.
The particular item I am talking about is called 'Ceiling Light 1x1' or something similar. It may be exclusive to World Adventures, I'm not sure, but I do not think so, since EA builders use it in practically every community lot they build. It provides a strong light source, just a couple of them spread over a room are usually enough to light it up perfectly.
Coloring your light sourcesThe next technique I'm now completely in love with is to give my light sources custom colors. I find the regular, white light that most lights give off both artificial-looking and ugly. Whenever you want a cooler light on something the defaults just won't do. Nor do any of the other presets, for example, selecting 'blue' will make the light 100% blue, which is a total overkill.
It's a good idea to save beforehand in case you don't like the results. Changing light colors cannot be undone by clicking 'undo.'
To give your light a custom color, hold Shift while you left-click it (in live mode) or hold CTRL + Shift, then left-click (in build/buy mode).
This can be done in live as well as in build/buy mode, but if you're using invisible lights like I am, you'll obviously need to do the latter.
A menu pops up. Select 'Change color' then 'Custom color' then 'This light,' 'This room,' or 'All lights,' depending on your preference.
Now you get to fill in a series of three numbers, separated by commas. These are RGB values. This means that you can look up the exact color you want in an RGB table like this:
http://www.rapidtables.com/web/color/RGB_Color.htm.
Cool colorsNow for a final treat, here are some of the very beautiful, cool light colors I've discovered through experimentation:
100,150,255 (Subtle cold light)
50,50,255 (Blue without overkill)
0,150,255 (The aquamarine used in some EA lamps)
I'm still trying to find out the exact RGB color of Sunset Valley moonlight. If anybody knows, please let me know. I made a home with open roof once and I've been obsessed with finding that color ever since.
Happy simming!